The invention relates to an device and method for sensing an object in a vehicle, particularly for occupant detection, and the use of the device and method for adjusting an element.
From the xe2x80x9c4th International Symposium and Exhibition on Sophisticated Car Occupant Safety Systemsxe2x80x9d of the Fraunhofer Institute for Chemical Technology there is known an occupant detection system wherein occupancy of a vehicle seat is detected using infrared optical technology, light spots being projected by an LED array via an optical system onto the seat area to be detected. Each of these light spots is in turn imaged onto a CCD array by means of a receiver lens. Different positions of the peaks on the CCD array are produced depending on the distance of the light spot. The distance is determined from the fixed geometry of the image sensor and the maximum position using a triangulation process, so that the interpolation points of a contour can be calculated in this way using a plurality of LEDs.
The disadvantage of a system of this kind is that the shape of an object on the vehicle seat, e.g. an occupant or child seat, can only be obtained with low resolution.
The invention performs position sensing of elements or objects in a vehicle.
On elements of the vehicle, e.g. on a vehicle seat, there is provided an optical marking. In a vehicle there is provided a camera which detects the marking(s). An evaluation unit is connected downstream of the camera and determines the positions of the markings.
The camera records spatial information of the image area to be captured, the camera possibly being implemented as a stereo camera (3D camera) with two image sensors whose optical axes have a predefined spacing.
A suitable camera is, for example, a 3D camera which supplies the contour of an object on a vehicle seat by means of a range image. The volume distribution of the object on the seat can be extracted from the contour of the object by subtracting the contour of the seat surface. This constitutes a very robust method for classifying the object into child seats and persons of different weight categories. For a method of this kind it is important to measure and store the surface (contour) of the unoccupied vehicle seat, so that the information is then available for determining the range image of the vehicle seat in the occupied state. However, the seats are mainly re-adjusted after being occupied by a person. From the position of the marking, e.g. on the vehicle seat, the evaluation unit can calculate the surface shape of the unoccupied element on the basis of the pre-defined dimensions of the relevant elements in the vehicle, e.g. the contour of the surface of the vehicle seat. Advantageously, this means that the surface shape of the vehicle seat is known, which advantageously provides easier and more reliable detection of an occupant or of a child seat using image processing algorithms.
Another element could conceivably be a child seat, a head restraint or a rear-view mirror.
Moreover, the evaluation unit can determine the position of the element from the position of the markings. The element can be moveable or fixed relative to the vehicle.
The markings can have a predefined geometrical shape in each case, e.g. punctual, lineal and/or area1. Thus, for example, a marking can have a characteristic shape and consist of a group of punctual, lineal or area1 markings.
A marking can be implemented as a reflector, e.g. a flat mirror, as a triple mirror which reflects the incident light by precisely 180xc2x0 relative to the light source, or as a spherical mirror which distributes the light from a light source over a predefined solid angle according to its curvature. A diffuse reflector with a high reflection factor is also conceivable.
In another embodiment, one of the markings is implemented as an opto-transmitter whose light is directly incident on the camera. The opto-transmitter can emit light in a predefined signal sequence by means of which each of the markings implemented as an opto-transmitter can be individually encoded.
The camera is preferably disposed on the lining of the vehicle roof. The brightness of the light reflected or transmitted by the marking is greater than that of the light reflected by the element in the immediate vicinity of the marking. This means that the camera can unambiguously sense the corresponding marking and determine its spatial position by means of gray-scaling and using image analysis processes running in the evaluation unit connected to the camera. If the marking is covered, no light from the marking is incident on the camera. This can additionally be analyzed and e.g. provide indications of seat occupancy, a child seat on the seat or a seat cover.
The light reflected or emitted by the corresponding marking is preferably at least twice as bright as the light reflected by the elements.
Using the above-mentioned device or method, the position of a rear-view mirror, vehicle seat or child seat, for example, can be detected. Detection of the position of the markings will support image processing methods for occupant detection, as the precise position of the vehicle seat, child seat or similar is therefore known. In addition, suitable image processing systems can now reliably ascertain the position of a vehicle occupant and discriminate e.g. between the vehicle seat and the body of the occupant. Classification of the occupancy state of the vehicle seat is therefore possible, which means that an airbag or a seat-belt restraint system can be deployed fully, partially or not at all according to the type of seat occupancy.
In addition, the position of the rear-view mirror and head restraint can be adjusted as a function of the determined position of the occupant, particularly the latter""s head position.
By extrapolation of the backrest onto the vehicle floor, the displacement and position of the entire seat can be ascertained relative to the vehicle floor.
In order to differentiate between the optically visible markings and light reflexes, the markings can be encoded either spatially, i.e. by a pattern, or on a time basis, i.e. by a characteristic signal correlated with the image rate. (n. o.)
As well as the range image, the camera also supplies a gray-scale image of the image area to be captured in the vehicle. An (x, y, z) position in the range image with a gray-scale image is assigned in each case, via a calculation method (algorithm) for determining a range image, to a position (x, y) of a respective image sensor using the gray-scale image assigned to the position. A position in the gray-scale image can therefore be assigned to a point on the contour of a element in the vehicle interior or to a marking.
Moveable markings can additionally be placed in relation to non-moveable markings, which means that the positions of the moveable markings can be detected faster and more reliably. Moveable elements are e.g. a sliding vehicle seat with head restraint and child seat or a rear-view mirror. Non-moveable elements in the vehicle are e.g. a dashboard, the windshield or the door trim panels.
Covering of airbags, e.g. front airbags and side airbags, can be detected by the optical markings being covered for a prolonged period of time. An appropriate warning that an airbag has been covered e.g. by a bag or a seat cover, can be issued to the driver. If markings important for the safety of the occupant are covered for a prolonged period, a visual or audible warning is issued to the driver.
The advantage of having markings on a vehicle seat is that it avoids disposing safety-relevant functions in the vehicle seat itself, e.g. position sensors for ascertaining the position of the vehicle seat, resulting in a simplification of the safety concept. A simple and reliable means, not hitherto achieved, of measuring the position of the seat back for inclination and position is likewise made possible without using additional sensors.
The system for determining the position of a vehicle seat can additionally be used as a position transducer for a person-related seat memory system, thereby obviating the need for a position transducer, external memory or external controller. Having optical markings on the surface of the seat and seat back can enhance safety by making it possible to verify whether the seat is empty or occupied. With the markings implemented time-coded as opto-transmitters, the robustness of the image recognition method can be advantageously increased if the markings are briefly or partially covered.
In addition, markings can be disposed on the seatbelt in order to determine the rolled-out belt length and to detect whether the belt has been put on.
With electrical window lifters, there is a risk of trapping an object, e.g. the head, neck, or parts of the arms of an occupant when the window is closed. An imaging method can be used to detect the upper edge of the window glass in the vehicle door. By providing a marking in the window glass, on the inner side of the window glass, on its upper edge or in its lower region, the position or the current height of the window glass can be determined. The above-mentioned imaging method allows an object to be detected between the upper edge of the window glass and the upper part of the window frame. In addition, determining a break between a marking or part of a marking in the case of areal markings indicates an object in the vicinity of the top edge of the window glasses (danger area). A marking can be incorporated in the window glass. Automatic closing of the window using an electric motor is controlled as a function of the detected position of the object and of the window height position, trapping of the object being preferably prevented by stopping or slowing down closure.